SAN FRANCISCO—At one time in Candlestick Park debate raged between Joe Montana or Steve Young at quarterback. Young seemed to wait forever before the team made a tough choice and gave him his chance.

Monday night in a 32-7 victory over the Chicago Bears, the San Francisco 49ers quarterback controversy was born again. Second-year quarterback Colin Kaepernick performed like a veteran in dismantling a Bears defense that was among the league's best all season. In fact, Kaepernick performed at least as well — or even better — than veteran Alex Smith, who sat out with the concussion that felled him a week earlier.

The result was a building groundswell of support for Kaepernick as a starter. Given the chance afterward to put a lid on the speculation, 49ers coach Jim Harbaugh did nothing more than throw fuel on the fires of speculation.

Kaepernick didn't know for certain he would even start until Monday morning, according to Harbaugh.

Kaepernick did take all the snaps on Saturday and in Sunday walk-through, but he played like someone who'd been running San Francisco's offense for a decade. He was 16-of-23 passing for 243 yards, two touchdowns and a 133.1 rating.

What the numbers didn't say was he called audibles and looked for secondary receivers like a 10-year veteran, while displaying an arm that explained how the Chicago Cubs could select him in the MLB draft.

"I felt real comfortable with what [the Bears] were doing and what we had in our game plan and things just kept rolling from there," Kaepernick said.

The idea that the 49ers would consider Kaepernick to start Sunday against the New Orleans Saints when Smith could be available seems a stretch. After all, Kaepernick, a 2011 NFL Draft second-round pick, has thrown 46 career passes.

It is possible Smith might not be ready, as he hasn't passed all the requirements before returning to the field from a concussion.

Harbaugh could have pointed this out and cautioned all against jumping the gun. He didn't.

"We'll make that decision as we go forward," Harbaugh said. "We'll make that decision when we have to make it."

If Smith had been suffering through a poor season, it might be a no-brainer. But Smith has a 104.1 rating on the season and completed 70 percent of his passes, with 13 TD throws to five interceptions.

On Kaepernick's side is the fact he looked so polished with so little preparation. He found tight end Vernon Davis six times for 83 yards and a touchdown after Smith connected with Davis nine times the previous four games combined — and Kaepernick did it looking so calm and collected.

"It was a little different because we didn't know how Alex was going to be," Kaepernick said. "We didn't know if it was going to be him or me. So it was a little bit difficult as far as trying to prepare both of us at the same time."

With scores in their first three possessions, the 49ers saw very quickly what Kaepernick could do.

"I wanted to come out and show what I was capable of and show I could be the starter and that's what I've been trying to prove," Kaepernick said.

What Harbaugh could do is start Kaepernick for another game or two while saying he's giving Smith time to heal. Home-field edge in the first round of the playoffs currently belongs to the 49ers, who are 7-2-1, and they've beaten both the Bears and Green Bay Packers, their closest pursuers. They're being pressured only by the Seattle Seahawks within the NFC West.

It's a situation that can provide the 49ers with a proven one-two quarterback punch going forward, in case Smith were to stumble in the playoffs and produce a game like he had earlier in a loss to the New York Giants.

Or it's a situation that could also have within it the seeds of destruction if improperly handled.

"It helps to have a great relationship," Kaepernick said. Smith "was the first one every time I came over to the sideline saying great job.

"Between us, we're just going to come in and work every day and we'll leave that up to the coaches."

In defense of Smith, it helped Kaepernick to no end to have a defense dominating the way Aldon Smith and company did against the Jay Cutler-less Bears. With six sacks of backup Jason Campbell, the Niners held Chicago to 143 net yards.

"Tonight was probably the worst nightmare," Campbell said.

The 49ers allowed 24 points to the Rams, but knew they had the kind of defense that could dismantle a Bears offensive line struggling to make the simplest blocks. What they didn't know is if their young backup quarterback had the ability to win his first NFL start.

They had an inkling of Kaepernick's talents from sporadic play in gimmicky read-option or Wildcat formations. There was nothing cheap about what he did Monday night, though. This came against a defense with possible Hall of Fame players Brian Urlacher and Julius Peppers, eight-time Pro Bowl linebacker Lance Briggs and cornerback Charles Tillman, who was being talked about as defensive player of the year before two consecutive Bears losses.

And Kaepernick dismantled them.

"He runs well, he throws it well," Urlacher said about Kaepernick. "He's fast, he makes good decisions.

"If he doesn't have it, he throws it away or he takes off."

The ingredients are all there for a successful quarterback, and also for a full-blown quarterback controversy.